This invention relates to a transmitting facility and a receiving facility for a multipoint-to-point synchronous CDMA network, and to an acquisition method for a multipoint-to-point synchronous CDMA network.
Multipoint-to-point CDMA networks (CDMA=code division multiple access) are being used increasingly for the implementation of upstream channels in interactive communications networks. Interactive communications networks are designed as HFC (hybrid fiber/coax) or HFR (hybrid fiber/radio) networks, for example. For the downstream channel, use is made of a point-to-multipoint network that contains an optical feeder followed by a coaxial-cable or radio network. The upstream channel is increasingly implemented using a multipoint-to-point network, e.g., a CDMA network, which can be designed as an optical, electrical, or radio network or as a hybrid network.
In a synchronous CDMA network with a center and a plurality of terminals, the terminals must be locked in frequency and phase to the master clock of the center. The master clock is transmitted over the downstream channel to the terminals, in which frequency synchronization and phase synchronization with phase correction are implemented using a phase-locked loop (PLL) to generate their individual clock signals. To achieve synchronization, each of the terminals transmits an acquisition signal over the upstream channel of the multipoint-to-point CDMA network to the center.
WO 97/08861 discloses an acquisition method in which acquisition signals are sent to the center in CDMA-coded form. The upstream channel is divided into a first time range, which is reserved for the transfer of information signals, and a second time range, which is reserved for the transfer of acquisition signals. Accordingly, the second range is not available for information transfer, so that the existing transmission capacity is not optimally utilized.